1. Field of the Invention
The present invention relates to negative electrode materials for rechargeable lithium batteries, and to rechargeable lithium batteries including the same.
2. Description of the Related Art
A conventional rechargeable lithium battery includes a LiCoO2 positive active material, a graphite negative active material, and a non-aqueous electrolyte. Rechargeable lithium batteries have been widely used as power sources for electronic devices such as cellular phones, digital still cameras, digital video cameras, and laptop computers. For the negative active material of a rechargeable lithium battery, carbon-based materials such as artificial or natural graphite, hard carbon, and so on, have been used.
Of the carbon-based materials, graphite has a low discharge potential of 0.2V compared with lithium, thereby increasing the discharge voltage and energy density of the battery. Therefore, a battery including graphite as the negative active material has a high average discharge potential of 3.6 to 3.7V and an excellent energy density. Furthermore, graphite is most comprehensively used of the aforementioned carbon-based materials since it guarantees better cycle-life for a battery due to its outstanding reversibility.
However, graphite has low density (i.e., a theoretical density of 2.2 g/cc). Thus, a negative electrode including graphite as the negative active material has low energy density per unit volume, consequently resulting in low capacity when used in a battery.
To address these problems, much research on oxide negative electrodes with high energy densities has been conducted. For example, a LiaMgbVOc (0.05≦a≦3, 0.12≦b≦2, 2≦2c−a−2b≦5) negative active material has been proposed.
A negative active material for a rechargeable lithium battery that includes a lithium vanadium composite oxide has also been proposed. The lithium vanadium composite oxide has a significantly lower discharge potential relative to lithium, thereby providing a rechargeable lithium battery having a high energy density. However, the lithium vanadium composite oxide undergoes an irreversible crystalline structure deterioration during charge and discharge, which causes decomposition of the electrolyte. As a result, the lithium vanadium composite oxide deteriorates the cycle-life of the battery.